Conventional punch presses are known for punching holes in and shaping flat panels such as flat sheet metal. In these punch presses, as shown in U.S. Pat. No. 4,343,210, the flat sheet metal panel is passed between upper tools and lower dies mounted on a punch press. As the workpiece is moved to a correct position, each tool punches a hole or forms a shape in the workpiece.
It is also known in the art to replace the punching tools of these workpieces with shaping tools which form a continuous shape, i.e., a groove or the like, in the flat sheet metal workpiece.
One way to form such an elongated shape is by nibbling. Nibbling is performed by a tool having a semi-spherical part and a recessed part between which the workpiece is positioned as shown in Japanese Patent No. 2247021. The tool performs a series of rapid short vertical strokes to form indentations, ultimately creating a groove in the workpiece. Tools of this type suffer from the drawback that the series of connected indentations which are formed are not nearly as smooth as a continuous groove formed by rollers.
Another known way to form a continuous shape is by using a tool having upper and lower parts with mating cylindrical rollers rotatable about parallel horizontal axes. Such tools are known, for example, from U.S. Pat. No. 5,555,759, which discloses a tool having upper and lower cylindrical rollers, rotatable about axes which are parallel to the workpiece to be treated, the workpiece being positioned between the rollers. A major drawback of this structure is that the workpiece can only be turned about a relatively wide arc since the rollers move linearly, thereby reducing the ability to make turns about a narrow arc. In other words, if the workpiece is turned about a narrow arc or point, the rollers will slide laterally, causing damage to the workpiece.